Crank Case Pressure

[minimikee]

Hey all,

I was doing an oil change today and while the engine was running and the filler cap off i noticed there was a lot of air passing out of the hole, as if the crank case was very highly pressurised ... I'm just curious if this is normal??

[SSS]

It's normal. Generally you have cause for concern if there is no pulsing of air through the filler cap.
On the other hand, too much pulsing is indicative of excessive blow-by, which is combustion pressure leaking past the rings.

Some do setup pressure sensors to log crankcase pressure at various load and rpms, these are usually guys running dry sump systems to record vaccuum in the crank case from the scavenging section of the drysump pump. Less vaccuum = ring sealing problems (usually).

[minimikee]

yeah my dad and i went for a drive yesterday and he didnt notice anything unusual out the exhaust even on hard acceleration.

Just seems like a like of pressure

[evlknvl]

You can opt for an oil catch can with one outlet venting to atmosphere and the other outlet connecting to a tee connection and then one to both the rocker cover and PC outlet above the oil pump. There are other ways of connecting this if running forced induction or for a more emission friendly setup.

[evlknvl]

Oh, and the catch can should be filled with steel wool to assist as a filter to only allow pressure to vent through the outlet and not oil also. And the outlet which vents to air from the catch can must have a filter on it like the rocker cover filters.

[minimikee]

yeah I've already got a catch can in place between the PCV and intake ... thats been there for a while though